Energy absorbing device

ABSTRACT

An energy absorbing device formed from an integral molded unit of an elastomeric material such as polyurethane. The unit is composed of an annular body portion having an elliptical configuration with relatively thick wall sections and a pair of impact elements projecting from the outer surface of the body portion at stations which lie generally along the minor axis of the elliptical configuration. The resilience of the body portion, and to a more limited extent the impacting elements, allows the device to absorb energy when objects strike the projecting ends of the impact elements.

United States Patent Vernon et al.

[451 Mar. 21, 1972 [54] ENERGY ABSORBING DEVICE [72] Inventors: John T.Vernon; Albert M. Ankrom, both of Charlotte, NC.

[73] Assignee: Rogers Corporation, Rogers, Conn.

[22] Filed: June 29, 1970 [2]] Appl. No.: 50,742

[52] U.S. Cl ..267/l52, 267/141 [51] Int. Cl ..F16f H44 [58] FieldofSearch ..267/l4 D, 141, 152, 153

[56] References Cited UNITED STATES PATENTS 3,236,513 2/1966 Nicolaisen..267/l53 3,230,880 1/1966 Beaver ..267/l53 Primary ExaminerJames B.Marbert AtmrneyFishman and Van Kirk 57 ABSTRACT An energy absorbingdevice formed from an integral molded unit of an elastomeric materialsuch as polyurethane. The unit is composed of an annular body portionhaving an elliptical configuration with relatively thick wall sectionsand a pair of impact elements projecting from the outer surface of thebody portion at stations which lie generally along the minor axis of theelliptical configuration. The resilience of the body portion, and to amore limited extent the impacting elements, allows the device to absorbenergy when objects strike the projecting ends of the impact elements.

8 Claims, 3 Drawing Figures Patented March 21,1972 3,650,520

PR/OR'ART L w 14 J w a ,|7 WA f 55 ggiu'j v45 45 INVENTORS JOHN T.VERNON ALBERT M. ANKROM ATTORNEYS BACKGROUND OF THE INVENTION 1. FIELDOF THE INVENTION This invention relates to the field of energy absorbingdevices and in particular the invention is directed to absorbing devicesof the type in which energy dissipation occurs through the deformationor working of an elastomeric material.

2. DESCRIPTION OF THE PRIOR ART Energy absorbing devices which employ anelastomeric material are already known in the prior art. Such devices,as shown in FIG. 1, are frequently composite structures including bothmetallic elements and a solid body of elastomeric material. Theprincipal energy absorbing component is the elastomeric material whichdissipates energy due to the inherent damping characteristics of thematerial. The metallic components provide a hard wear surface which isintended to withstand the high impact loads and abrasive action at theinterface between an impacting object and the absorber.

The composite absorbers, however, suffer several disadvantages. Themetallic element, while providing a hard wear surface. becomes brittlewith usage due to the cold working of the metal. The cold working isparticularly noticeable where the impacting component is also metallicand therefore less likely to attenuate the shock loads during impact.Continued cold working ofthe metallic elements results in fracture ofthe embrittle elements or continued chipping and flaking at the impactsurface. This destruction of the elements may require replacement atfrequent intervals during periods of heavy and continuous use.

The composite absorbers with metallic members which contact an impactingobject are not only subject to wear themselves, but also produce wear onthe impacting object. Metalto-metal contact may cause abrasion on bothof the metallic pieces. Replacement of both metallic pieces maysignificantly increase the operating costs of a machine which employsthe composite absorbers. Still further, the composite absorbers arefrequently more expensive due to the multi-piece construction of thedevices. Both the metallic elements and the elastomeric material must bemanufactured separately and subsequently assembled before the completeenergy absorption device is formed.

SUMMARY OF THE INVENTION The present invention overcomes the severaldisadvantages of the prior art devices by constructing an energyabsorbing device in the form of an integral molded elastomeric unithaving impact elements and an annular body portion. The annular bodyportion flexes upon impact on the impact elements, thus imparting aneffect similar to compression to a body of essentially incompressiblematerial. The elastomeric impact units do not suffer from cold workingand do not damage the elements impacting on them.

It is accordingly an object of the present invention to provide anenergy absorbing device which is formed in an integral unit.

It is a further object of the present invention to provide an energyabsorbing device which is not subject to cold working and brittlefracture after extended use.

It is another object of the present invention to provide an energyabsorbing device which is relatively inexpensive to manufacture whencompared with composite energy absorbers known in the prior art.

It is still a further object of the present invention to provide anenergy absorbing device having an annular flexible body portion for loaddissipation.

It is still a further object of the present invention to provide anenergy absorbing device composed entirely of an elastomeric material. i

It is still a further object of the present invention to provide anenergy absorbing device which reduces the amount of wear on objectswhich impact on the device.

BRIEF DESCRIPTION OF THE DRAWINGS The novel elastomeric energy absorbingdevice of the present invention together with its numerous objects andadvantages will be better understood by reference to the followingdrawings in which corresponding elements bear the same referencenumerals through the several figures.

FIG. I is a cross-sectional view of a composite energy absorbing deviceknown in the prior art.

FIG. 2 is a perspective view of the elastomeric energy absorbing deviceof the present invention.

FIG. 3 is a cross-sectional view of a machine showing a typicalinstallation and working environment for the novel energy absorbingdevice.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to more clearlyunderstand the present invention, it is appropriate to briefly examinethe energy absorbing devices which form a part of the prior art. FIG. 1discloses a damping or energy absorbing device which has been employedin the past in the same environment as that contemplated for the novelenergy absorbing device of the present invention. The prior artabsorber, generally designated by the numeral 10, is a composite of bothmetallic and elastomeric pieces. The absorber 10 includes hardened metalinserts 12 and 14 which are mounted in an elastomeric support 16. Thesupport 16 is a molded structure and has a spherical shape with recesses18 and 20 at diametrically opposite stations on the spherical surface.The recesses 18 and 20 are sized to receive the inserts 12 and 14 andhave a depth which permits a substantial portion of each insert toproject well above the spherical surface.

In operation, the absorber 10 is supported in a fixture so that themetal inserts project outwardly as stops. When an object impacts on theprojecting end of the insert, energy is transmitted by the insert to thesupport 16 where dissipation takes place. The inserts 12 and 14 aredisposed on opposite sides of the support 16 so that two differentobjects can approach the absorber simultaneously and dissipate thekinetic energy of the objects within the support 16 without transmittingloads to a mounting fixture holding the support.

If the absorber 10 is embodied in a machine where the projecting ends ofthe inserts 12 and 14 are continuously subjected to impacting objects,cold working of the metal at the projecting ends causes embrittlementand subsequent fracture of the inserts. Continuous replacement of theinserts due to the fractures renders the operation of the machine moreexpensive in view of both lost operating time and the repair costs.Furthermore, the metallic objects which impact on the inserts are alsosubject to rapid wear because of the metal-tometal contact which occursunder the severe impact conditions.

FIG. 2 reveals the novel elastomeric energy absorbing device of thepresent invention in a preferred embodiment. The device, generallydesignated by the numeral 30, differs in several respects from the priorart device of FIG. 1. One of the principal features of the device 30 isthat it is composed completely of an elastomeric material such aspolyurethane elastomer. Such resilient materials can be formed intointegral elements by a simple molding process. In the integral form, theabsorber 30 is constructed in substantially fewer steps than the device10 in FIG. I. Since the molding of the support 16 or the entire device30 entails substantially the same steps, the manufacturing stepsconcerned with constructing and inserting the metal inserts 12 and 14,which constitute additional operations and add to the cost of the priorart device 10, are eliminated.

In examining the new and improved energy absorbing device 30, severalimportant structural distinctions aside from its integral form are to benoted. The device 30 is composed of an annular body portion 32 which iscentrally disposed between two projecting legs 34 and 36. The annularbody portion 32 forms a complete ring having a generally ellipticalconfiguration in the unloaded condition shown in FIG. 2. The bodyportion 32 has a thick wall section which limits the central aperture 38to a relatively narrow elliptical configuration. The heavy wall sectionof the body portion 32 is provided because the elastomeric materialwithin the walls forms the principal element for dissipating energy. Thecentral aperture 38 is important, however. The aperture allows device 30to deform and also isolates shock loads applied to one side of theabsorber from the other side.

Elastomeric legs 34 and 36 are disposed at diametrically oppositestations on the outer surface of the body portion 32. With respect tothe elliptical configuration of the body portion 32, the legs 34 and 36are positioned near the minor axis 40 of the ellipse and projectgenerally in a direction parallel to the minor axis. As mentioned above,the device 30 is made in an integral form and therefore the legs 34 and36 consist of the same elastomeric material as the body portion 32. Theintegral construction eliminates the possibility of the legs falling outof the body portion and does not require special connecting materialbetween the legs in the body portion.

Since legs 34 and 36 are also formed of an elastomeric material, anadditional energy absorbing element is available in the device 30 incontrast to the prior art absorber 10. Even though elastomericmaterials, such as polyurethane, are basically incompressible mediums, acertain amount of damping is provided by the leg and this additionalamount of resiliency may result in a substantial reduction in the levelof shock loads when the absorber performs its energy-dissipatingfunction.

Legs 34 and 36 possess impact surfaces 42 and 44, respectively, whichlie in a plane generally perpendicular to the axis 40. It will bereadily understood that the impact surfaces 42 and 44 present asubstantially softer impact surface than the corresponding surfaces ofmetal inserts l2 and 14 in FIG. I. As a consequence, when an objectimpacts on the device 30 the possibility of abrasion occurring betweenthe legs and the object is negligible. Accordingly, less wear on theimpacting object takes place. Even though the abrasive aspects of thedevice 30 are ameliorated, the essential energy absorbing feature isretained. In transmitting energy through either of the legs, a limitedamount of deformation with shear is experienced. The body portion 32,however, provides the principal source of energy dissipation.

Slnce legs 34 and 36 are formed from an elastomeric material, thecontinuous impacting of objects on surfaces 42 and 44 does not result inembrittlement of the legs; therefore, no fracture failures areexperienced as in the prior art devices. The use of an elastomericimpact element, such as leg 34, in place ofa metallic insert, such asinsert 12 in FIG. 1, provides not only increased deformation but alsoeliminates the type of failures experienced in the prior art devices.

In FIG. 3 the novel energy absorbing device 30 is disclosed in a workingenvironment. While the device 30 can be employed in numerous machinesand structures, the apparatus shown in FIG. 3 represents a portion of apin drafter such as that made by the Warner Swazey Co. of Cleveland,Ohio. Such apparatus is employed in fiber processing machines forcombing long staple fibers. The pin drafter has a stationary slide 50and two movable follower bars 52 and 54. The follower bars 52 and 54carry combs (not shown) and are continuously translated in a generallyrectangular path indicated by the arrows 56 and 58 to pull the combsthrough the fibers. In traversing the generally rectangular paths, thefollower bars 52 and 54 impact simultaneously on opposite sides of theslide 50. After reaching the impact position, the bars 52 and 54 aretranslated along the surfaces of the slide as indicated by the phantomposition of the bars. Since the combing operation forms no part of thepresent invention, the details of the mechanism which translates thefollower bars is not shown.

The energy absorbing device 30 is mounted in the hollow central portionof the slide 50 at the impact position of the bars 52 and 54. The device30 is held in the slide 50 by means of cut-outs 60 and 62 through whichthe legs 34 and 36 respectively project. The cut-outs 60 and 62 areslightly larger than the legs 34 and 36 so that no binding occursbetween the slide 50 and the legs. With ample clearance, none of theimpact load will be transmitted to the slide 50 and energy dissipationwill occur within the device 30 itself.

The function of the central aperture 38 in the body portion 32 is moreclearly understood from the installation shown in FIG. 3. As the twofollower bars 52 and 54 impact on the legs 34 and 36, the elastomericbody portion 32 is allowed to deflect inwardly toward the centralaperture 38. If the two bars 52 and 54 strike the absorbing devicesimultaneously, the energy is absorbed entirely within the device 30. Ifthe two follower bars are not moving toward the slide 50 withsubstantially the same energy, aperture 38 isolates onehalf of theabsorber from the other half so that energy is not transmitted throughthe absorber to the opposite follower bar. The aperture 38 thereforeprovides both resiliency and isolation.

While the absorber is shown in FIG. 3 as performing a dual function,that is operating with two impacting objects, it will be readilyunderstood that the energy absorbing device can operate equally as wellwhere only a single object impacts on one of the projecting legs. Insuch circumstances, it may be sufficient to provide only one leg on theouter surface of the annular body portion 32. Other modifications to thestructure of the device 30 can also be made without departing from thespirit of the invention. For example, the precise ellipticalconfiguration of the body portion 32 may be varied to change the energyabsorbing characteristics of the device. The dimensions of the bodyportion including the size and dimensions of the wall sections may bevaried to suit particular functions. It is similarly feasible to employa wall section for the body portion which is other than the generallyrectangular shape in cross section as reflected by the embodiment inFIG. 2. Oval or circular sections may be employed with equal advantage.Likewise, the shape of the legs can be varied for special functions.Accordingly, the novel energy absorbing device 30 has been disclosed inone preferred embodiment for purposes of illustration rather thanlimitation.

What is claimed is:

1. An energy absorbing device comprising:

an annular body portion composed of an elastomeric material; and

at least a first impact element projecting outwardly from the outersurface of said body portion, said impact element being integral withsaid body portion and composed of the same elastomeric material as thebody portion.

2. The elastomeric energy absorbing device of claim 1 wherein:

the elastomeric material forming the integral body portion and impactelement is a molded polyurethane elastomer.

3. The energy absorbing device of claim 1 wherein:

the annular body portion has a central aperture with a generallyelliptical configuration with the device in the unloaded condition.

4. The energy absorbing device of claim 3 wherein:

the impact element projects outwardly from the body portion at a pointon the outer surface of the body portion which lies substantially alongthe minor axis of the elliptical aperture.

5. The energy absorbing device of claim 1 wherein:

a second integral impact element projects outwardly from the outersurface of the annular body portion, said second impact elementextending from the outer surface of the body portion at a positionremote from the first impact element and being composed of theelastomeric material forming the body portion.

6. The energy absorbing device of claim 5 wherein:

the second impact element is located on the outer surface of the annularbody portion at a position generally diametrically opposite the firstimpact element.

7. The energy absorbing device of claim 6 wherein:

the annular body portion has an elliptical configuration; and

the first and second impact elements are disposed on the outer surfaceof the body portion at positions lying substantially on the minor axisof the elliptical configuration and project along the minor axis. 8. Theelastomeric energy absorbing device of claim 7 wherein the elastomericmaterial forming the integral body portion and impact elements is amolded polyurethane. 5

1. An energy absorbing device comprising: an annular body portioncomposed of an elastomeric material; and at least a first impact elementprojecting outwardly from the outer surface of said body portion, saidimpact element being integral with said body portion and composed of thesame elastomeric material as the body portion.
 2. The elastomeric energyabsorbing device of claim 1 wherein: the elastomeric material formingthe integral body portion and impact element is a molded polyurethaneelastomer.
 3. The energy absorbing device of claim 1 wherein: theannular body portion has a central aperture with a generally ellipticalconfiguration with the device in the unloaded condition.
 4. The energyabsorbing device of claim 3 wherein: the impact element projectsoutwardly from the body portion at a point on the outer surface of thebody portion which lies substantially along the minor axis of theelliptical aperture.
 5. The energy absorbing device of claim 1 wherein:a second integral impact element projects outwardly from the outersurface of the annular body portion, said second impact elementextending from the outer surface of the body portion at a positionremote from the first impact element and being composed of theelastomeric material forming the body portion.
 6. The energy absorbingdevice of claim 5 wherein: the second impact element is located on theouter surface of the annular body portion at a position generallydiametrically opposite the first impact element.
 7. The energy absorbingdevice of claim 6 wherein: the annular body portion has an ellipticalconfiguration; and the first and second impact elements are disposed onthe outer surface of the body portion at positions lying substantiallyon the minor axis of the elliptical configuration and project along theminor axis.
 8. The elastomeric energy absorbing device of claim 7wherein the elastomeric material forming the integral body portion andimpact elements is a molded polyurethane.